Assimilation of observations from
the Microwave Humidity Sounders on board
China’s FY-3B and FY-3C Meteorological Satellites
ITSC-20
Fabien Carminati
Katie Lean∗
William Bell
Nigel Atkinson
Met Office
*now at ECMWF
October 28, 2015
Introduction: Who we are
The Met Office (MO) Satellite Radiance Assimilation Group (SRAG)
I
Manage Infrared and Microwave sounding data from:
AIRS, ATOVS, ATMS, CrIS, IASI, and SSMIS.
I
Maintain processing system for operational assimilation
into the MO models.
I
Carry out research to improve and extend data applications.
I
Investigate the introduction of new instruments. Here, the MicroWave
Humidity Sounders (MWHS) on board China’s FY-3 platforms.
This work is supported by the European Horizon-2020 GAIA-CLIM
project and the CSSP:China program, in collaboration with the
NSMC-CMA.
2 / 13
Introduction: Source of data
Sounding missions supporting NWP and climate monitoring.
USA
Europe
China
FY-3 polar orbiting satellites will become a major source of data for
NWP and climate monitoring over the next decades.
3 / 13
Content
1. Presentation of MWHS-1 and -2
2. NWP-based assessment outlines
3. Assimilation experiments outlines
4. Concluding remarks
4 / 13
Presentation: FY-3B MWHS-1
Channel Number
MWHS-1 MWHS-2 ATMS
1
16
2
3
4
5
6
7
8
9
1-2
10
17
3
11
22
12
21
4
13
20
14
19
5
15
18
MWHS-1
150 (V-H)
183 ± 1.0 (V)
183 ± 3.0 (V)
183 ± 7.0 (V)
Frequency (GHz)
MWHS-2
89 (H)
118.75 ± 0.08 (V)
118.75 ± 0.2 (V)
118.75 ± 0.3 (V)
118.75 ± 0.8 (V)
118.75 ± 1.1 (V)
118.75 ± 2.5 (V)
118.75 ± 3.0 (V)
118.75 ± 5.0 (V)
150 (H)
183 ± 1.0 (V)
183 ± 1.8 (V)
183 ± 3.0 (V)
183 ± 4.5 (V)
183 ± 7.0 (V)
ATMS
88.2 (V)
165.5 (H)
183 ± 1.0 (H)
183 ± 1.8 (H)
183 ± 3.0 (H)
183 ± 4.5 (H)
183 ± 7.0 (H)
FY-3B equator crossing time: ∼14:20 local time ascending.
5 / 13
Presentation: FY-3C MWHS-2
Channel Number
MWHS-1 MWHS-2 ATMS
1
16
2
3
4
5
6
7
8
9
1-2
10
17
3
11
22
12
21
4
13
20
14
19
5
15
18
MWHS-1
150 (V-H)
183 ± 1.0 (V)
183 ± 3.0 (V)
183 ± 7.0 (V)
Frequency (GHz)
MWHS-2
89 (H)
118.75 ± 0.08 (V)
118.75 ± 0.2 (V)
118.75 ± 0.3 (V)
118.75 ± 0.8 (V)
118.75 ± 1.1 (V)
118.75 ± 2.5 (V)
118.75 ± 3.0 (V)
118.75 ± 5.0 (V)
150 (H)
183 ± 1.0 (V)
183 ± 1.8 (V)
183 ± 3.0 (V)
183 ± 4.5 (V)
183 ± 7.0 (V)
ATMS
88.2 (V)
165.5 (H)
183 ± 1.0 (H)
183 ± 1.8 (H)
183 ± 3.0 (H)
183 ± 4.5 (H)
183 ± 7.0 (H)
FY-3C equator crossing time: ∼10:20 local time descending.
6 / 13
Assessment: August 2015
(MWHS-1, -2, and ATMS)
First guess departure from raw observations (O-B), corrected observations (C-B)
and 1σ standard deviation
(K)
O-B Departures
C-B Departures
6
2
3
1
0
0
-3
-1
-6
-2
118.75 GHz
ATMS
MWHS-1
MWHS-2
7 / 13
183 GHz
Channel Number
MWHS-1 MWHS-2 ATMS
3
11
22
12
21
4
13
20
14
19
5
15
18
118.75 GHz
First Guess
MWHS-1
-1.416±2.346
-1.254±1.417
-0.034±1.509
183 GHz
Departure (O-B) ±1σ (K)
MWHS-2
ATMS
-1.026±1.629 0.949±1.533
-1.313±1.509 0.029±1.431
2.474±1.080 -0.138±0.923
4.915±1.400 -0.256±0.879
-1.980±1.028 0.562±0.838
Assessment: Corrected observations
August 2015 corrected observations from 1D-Var static bias correction
Channel Number
MWHS-1 MWHS-2 ATMS
3
11
22
12
21
4
13
20
14
19
5
15
18
First Guess
MWHS-1
-0.096±2.294
0.066±1.261
0.084±1.166
Departure (C-B) ±1σ (K)
MWHS-2
ATMS
0.055±1.621 0.029±1.528
0.048±1.498 0.036±1.429
0.326±1.028 0.061±0.916
0.348±1.027 0.050±0.859
0.289±0.994 0.020±0.827
Apr-Jun 2015∗ corrected observations from 4D-Var VarBC
Channel Number
MWHS-1 MWHS-2 ATMS
3
11
22
12
21
4
13
20
14
19
5
15
18
∗
8 / 13
First Guess
MWHS-1
-0.009±2.143
0.016±1.228
0.011±1.333
Departure (C-B) ±1σ (K)
MWHS-2
ATMS
-0.095±1.483 0.011±0.886
-0.080±1.378 -0.001±0.849
-0.036±0.909 -0.025±0.916
-0.011±0.910 -0.050±1.253
0.023±0.949 -0.070±1.336
two different trials: 62 days for MWHS-1 and 79 days for MWHS-2 and ATMS
Assimilation experiments
MWHS-1 and -2 are integrated into a full system, low resolution (N320),
for assimilation experiments in the MO global system.
I
Exp 1 MWHS-2 with static bias correction scheme . . . . . . . . . . 49 days long
I
Exp 2 MWHS-2 with variational bias correction scheme . . . . . 23 days long
I
Exp 3 MWHS-1 with variational bias correction scheme . . . . . 62 days long
Channel number
MWHS-1 MWHS-2
1
2-9
1-2
10
3
11
12
4
13
14
5
15
Observation errors (K)
MWHS-1 MWHS-2
7.67
3-6
5
5
4.5
4.5
4
4
4
4
4
4
Assimilated channels
Sea Sea-ice Land
NO
NO
NO
NO
NO
NO
NO
NO
NO
YES
NO
NO
YES
NO
NO
YES
NO
NO
YES
NO
NO
YES
NO
NO
Cloud screening
Bennartz rain∗ Cirrus cost
Rejected
Rejected
Rejected
Rejected
Rejected
Rejected
Rejected
Rejected
∗
9 / 13
only for MWHS-2
Assimilation experiments
Change in standard deviation of the fit to the model background for
MHS-NOAA19 (relative to the control).
Exp 1
Exp 2
Exp 3
(MWHS-2 with static bias correction)
(MWHS-2 with VarBC)
(MWHS-1 with VarBC)
10 / 13
Assimilation experiments: Exp 1
(MWHS-2 with static BC)
Similar improvement for other sounders in Exp 1 (and 2) ...
11 / 13
Assimilation experiments: Exp 3
(MWHS-1 with VarBC)
... But mixed picture in Exp 3.
Significant degradation in Relative
Humidity in lower and
mid-troposphere.
Exp
Control
12 / 13
Assimilation experiments: Exp 3
(MWHS-1 with VarBC)
Could we indirectly introduce bad data? (Hypothesis)
1D-Var RH – RHbg
12 / 13
Concluding remarks
I
MWHS-2 (likely) to be operationally assimilated in the next MO
system update.
I
MWHS-1 operational use postponed until we work out RH issues.
Future work
I
Further investigate MWHS-1 impact on relative humidity.
I
Test the assimilation of MWHS-1 and -2 183 GHz over land.
I
Test MWHS-2 118 GHz channels.
13 / 13
c Crown copyright
Supplementary material: Errors
Channel Number
MWHS-1 MWHS-2
1
2
3
4
5
6
7
8
9
1
2
10
3
11
12
4
13
14
5
15
14 / 13
NE∆T (K)
MWHS-1 (2x2) MWHS-2 (3x3)
0.14
1
0.37
0.32
0.3
0.28
0.28
0.17
0.2
0.30
0.29
0.15
0.37
0.25
0.2
0.20
0.16
0.13
0.19
0.15
Observation errors (K)
MWHS-1 MWHS-2
7.67
4
3
3
4
4
4
6
6
5
5
5
4.5
4.5
4
4
4
4
4
4
Supplementary material: Humidity Jacobian
200
200
300
300
Pressure [hPa]
Ch.11
400
500
400
Ch.12
Ch.13
500
Ch.14
600
600
Ch.15
700
700
800
800
900
900
1000
1000
−2.0
−1.5
−1.0
−0.5
0.0
Humidity Jacobian [K/(10%)]
15 / 13
Supplementary material: RH correlation
RH - RH background in analysis
16 / 13
Supplementary material: Long term variability
17 / 13
Supplementary material: Recent variability
18 / 13